Soldering iron



W. A. HAYES El AL Oct. 29 1940.

SOLDERING IRON Filed June 8, 1938 INVENTORS maze A. HA YES {555, 19 C Er'A/v dr @2013 AT ORNEY Patented Oct. 29, 1940 UNITED STATES PATENT OFFICE 2,219,649 SOLDERIN G IRON Wilbur A. Hayes and Joseph C. Ryan, Buffalo, N. Y., assignors to Colonial Radio Corporation, Buflalo, N. Y.

Application June 8, 1938, Serial No. 212,466 Claims. (01. 219-26) This application relates to soldering or like Clearly, it is undesirable for operators to have irons, and more particularly to such irons arto interrupt work to allow the iron to recover ranged to be electrically heated. satisfactory soldering temperature, and it is Electrically heated soldering irons have been equally undesirable for a manufacturer to have siderable period, and it might be supposed that each operator.

tools which are so widely used commercially Conventional irons are unsatisfactory for still would have attained a high order of efliciency. another reason. The usual type of iron re- An investigation of such irons made by us and sembles a screw-driver in shape, and while this which we believe included all conventional irons shape is very convenient, and is sometimes most 10 indicated, however, that the design and con-' desirable for certain types of work, for other struction thereof left muchto be desired. types it is awkward and excessively time-con- One of the most serious drawbacks which we suming for. the operator to use, and a so-called have found in such conventional irons is poor pistol grip is more easily used.

5 temperature or heat regulation, that is to say, With these points in mind, we have provided 16 extreme fluctuation of tip temperature with load, a soldering iron which gives very satisfactory and which may be regarded as somewhat analoresults. Time studies on soldering irons embodygous to voltage regulation of an electric generator ing our invention have shown that our irons are with changes in load. This poor regulation evimuch more efiective in steady soldering opera- 20 dences itself by an excessive rise in tip temperations than conventional irons of greater power 20 ture when the iron is running idle and by an rating. With the foregoing in mind, it may be excessive drop in tip temperature under load. noted that among the objects of our invention It.might be supposed that a drop in tip ternare: perature under load could be overcome by gen- To provide asoldering iron which will not reach erating a greater amount of heat in the heating excessive tip temperatures when running idle, 25 element. However, our investigation has shown even though burning steadily, and which also will that irons which exhibit poor regulation are not maintain a sumciently high tip temperature to design and construction of the iron itself, and above set forth which does, not require therm0- 30 in it.

In one case with a conventional iron, we found of whether it is running idle or under steady that with an extremely high internal heating eleload.

ment temperature, only approximately 300 be- To provide an iron of the class described which 35 ow t melting point of c pper, after five minwill be relatively simple and inexpensive to man utes of load, the tip temperature dropped to ufacture and in which replacements or changes 860 F., but when the iron was running idle, the of tip and heating element may be easily and temperature rose to over 1300 F., a temperature quickly effected.

which is sufficient to burn off he tinn ng0n the To provide a soldering iron of the class desired tip in about five seconds, and causes rapid dehaving a handle so arranged that the same may terioration the p itself. For most purposes be adjusted so that the handle is coaxial with the tip temperature should not exceed 850 F. the iron, or may be adjusted to form a pistol grip w e d a d Should not p Substantially in which the position of the grip with respect to V low 600 in five minutes while continuously heatthe body of the iron may be varied while still 45 ing a thermal load of 0.220 B. t. u. maintaining the same angular relation between Tim ie m n e rs using conventhe center line of the handle or grip and the centional irons show that considerable time is lost t r line of the iron.

by the operator bec se the dr p in ip tempera- .Still other objects and advantages of our inture under load reaches such apoint that effective vention will be apparent from the specification. 50 Soldering is impossible, this requiring the ep In this application we have particularly pointed or i r to t p W k to l t the ir n un idl out and distinctly claimed the part, improvement to temperature recovery, or to use two irons alor combination which we believe to be our inventernately, one recovering while the other is betion or discovery and we have explained the prinm used. ciples thereof and the best mode in which we 55 have contemplated applying those principles, so as to distinguish our invention from other inventions.

In the drawing- Fig. l. is'a side elevation, partly in sectign, of a soldering iron according to our. invention, one position of the handle being shown in full lines and two alternative positions being shown in dotted lines. I

Fig. 2 is a section on lines 2-2 of Fig. 1.

Fig. 3 is a section on lines 53-3 of Fig. 1.

Fig. i is a set of temperature-time curves of a conventional soldering iron and of a soldering iron according to our invention taken under identical conditions and showing the efiect of our invention.

Referring now more specifically to the drawing, i represents a heating element of any suitable type and power rating for the particular work required. Since heating elements are commercially available on the market in the form of rods and may be purchased under various trade names, they are not described in detail. The heating element i may be provided with screw threads engaged in corresponding screw threads 3 in the interior of the body 2, which may be axially drilled and the outer end tapered to form a conical seat i for the tip E, which is preferably given a conical taper ii to engage the-conical seat 6.

This seat and the taper oi the tip are made relatively long so as to give a large contact area between tip and body, in order to reduce the thermal resistance of the heat flow path from the body'to the tip.

The material and surface oi the body 2 are of great importance in lotaining good regulation. Since in actual soldering, heat is not withdrawn from the tip continuously, but intermittently, the body or the iron should have as high a thermal inertia as possible, consistent with other factors entering into the design, such as weight, bulk, balance, etc. This provides a thermal ei iect analogous to wheel on an engine, perature diiierential running.

In conventional irons it is customary to provide a thermal inertia in the iron or from to M. B. t; u. per F., although some irons have a thermal inertia of as little as 12, with power inputs ranging from 60 to 200 watts. in irons according to our inertia of a much larger order, which may be as high as too M. E. t. u. per F., in which case, with 150' watts input, we have found that the tip temperatur does not exceed approximately 715 F. when running idle and that the drop in tip temperature supplying a constant load of 0.220 B. t. u. for five minutes does not exceed approximately 115".

For most satisfactory results in a heavy duty iron with a heating element of 120 watts, we prefer to provide a thermal inertia of approximately 186. This gives an idle tip temperature not exceeding 900, and a tip temperature not substantially less than 700 after five minutes of supplying a constant load of 0.220 B. t. u. For ordinary work, that is, not heavy duty, we prefer that the thermal inertia should be approximately 66, with a heating element of 90 watts, this iron developing an idle tip temperature of approximately 780 to 790 F. and a tip temand reduces the tip tem= between idle and loaded perature of approximately 580 F. after five min utes of supplying a constant load of 0.230 B. t. u.

the mechanical efieet of a fiy invention we provide a thermal To minimize heat loss by radiation and thereby increase efiiciency, the surface of body 2 should have a bright or polished finish which it should retain under conditions of use. Various materials were tried and found unsuitable for 5 various reasons, such as corrosion of surface under use (which increases heat radiation and thereby reduces the eific-iency and likewise the regulation to a considerable extent), insuificlent thermal inertia, which likewise causes poor reg- 1 ulation, and it was finally found that a very satisfactory material from all standpoints is aluminum or aluminum alloy.

For example, the thermal inertia of bronze is 61 where 1 is the weight of the-body in ounces and 6 the thermal inertia factor of bronze; the thermal inertia of copper is 6.261,; the thermal inertia of stainless steel is 101 and the thermal inertia of alurnlnumis 16.251 The specific heat of aluminum is 0.26 gram calories per gram per degree centlgrade. The latter is easily machined and, although relatively soft so that it scratches easily if carelessly handled, is easily buffed and brought back to a bright finish and the surface finish stands up well under heat. Also, it has a low weight for given volume, and relatively low cost for given volume.

A further advantage is that while the tip (usu ally copper) is held firmly in position when hot,

yet when cool the tip may be easily indexed; that is to say, rotated in its seat to a particular angle with the body, and both tip and heater are easily replaced, there being little or no tendency for them to "freeze into the body.

The improvement in performance which our invention provides is clearly shown in Fig. i, in which the dotted line curve is a regulation curve of a typical conventional iron or? 100 watt rating, and the solid line curve is a regulation curve of an iron embodying our invention using a 90 watt 40 heating element, these curves being taken both for the heating and cooling cycles. In taking these curves, the current was turned on and the iron allowed to burn idle until the tip temperature had reached a constant value. a

At this point a calorimeter representing a load of 0.220 B. t. u. was applied to the tip and temperature readings were taken for five minutes, at which time the calorimeter was removecl and the iron allowed to recuperate for a period of ten minutes and the temperatures plotted, the tip temperatures being taken during this period also. The same procedure was followed with irons according to this invention.

These curves form a loop at the left of the figure analogous to a hysteresis loop and the shape and form of this loop is an excellent indicator of the regulating quality of the iron. It the loop is relatively wide and considerably inclined to the horizontal axis, it indicates a large differential between idle and load temperature and poor regulation.

In the conventional, iron curve it will be noted that this temperature difierential was equal to 400 F. approximately. On the other hand, it will be seen that the iron embodying our inventlon, shows a very fiat loop having a small inclination to the horizontal axis, and has a difierentlal of only 200 F. between idle and load tip temperatures. This is very satisfactory reg- 7 ulation, and means in operation high thermal emciency, maximum soldering efficiency, and maximum life of tip and. heater element. It will be noted that although our iron draws ten watts less than the conventional iron, under load it extending projection 2| through nearly maintains a tiptemperature 200 that'of the conventional iron- The handle of the iron is preferably secured to the extending portion 8 of the heating elehigher than which the iron may be hung up conveniently near the operator when solderingis interrupted.

The two ends ofthe clamp Hi may be riveted the axis of the body 2.

These links may be riveted or otherwise secured together as at I 8 arms l9 extending from bracket 20 which may be suitably secured about a rectangular upwardly 20 being secured to the projection 2| in any desired manner, as for example, by bolts or screws 23 extending therethrough. Spacer element 24 may surround bolt 25 and spacing washers 28 ,p

, a manner similar to the joint at the opposite end of linksl3 and II to provide a friction adjustment of the axis of the grip, 28 with reference to links H and I3.

By the provision of it will be seen that links I! and H can be swung and for any position of links I! and M the grip 1. In an electrically heated tool of the classdescribed, in combination, a copper tip, a tubular aluminum body, an electrical heating element in the form of a readily removable rod. positioned making direct and intimate contact with the interior wall of said body, said aaiae-ia ody having a and may then diverge to engage.

from grip 22; the bracket these Joints and the links on the Joint with clamp l0- as indicated by the dotted line position in Fig, 1,.

-' adjustable with respect "grip being angularly adjustable with respect to.

t 3 tapered conical opening in the end thereof for receiving said tip, and said tip having a conical tapered portion to engage the opening in said body.

2. In an electrically heated tool of the class load tip temperature.

3. In an electrically heated threaded from the opposite end to receive a heatscrew-threaded heating el'esubstantially worse than 25% temperature.

4. In an electrically heated tool of the class described, in combination, a tip to be heated, said ment. positioned longitudinally 'vvithin said ahandle, a link connection from said handle to said body, said link connection being angularly to said body and said said linkconnection.

5. In an electrically heated tool of the class I described, in combination, a tip to be heated for supplying heat to the work, said tip having a conical seat portion, a body in the form of a cylinder, said body having a conicri seat in one end thereof to, receive said tip to permit quick indexing thereof in the form of a unitary, readily removable rod, and making direct contact with the interior surface of said body, a heating element positioned within said body and extending longitudinally thereof, a member secured to said grip and having'a pivot ofl'set axially thereof, a second member secured WILBUR A. HAYES. JOSEPH RYAN.

tool of the class bodydO 

